φυλακή (phulakē)

The noun phulakē carries a core meaning of guarding or watching, but in Scripture it most commonly refers to the place where those under guard are kept: a prison. This usage appears frequently in the Gospels and Acts, describing where Jesus’ forerunner John was held (Luke 3:20) and where the apostles were confined before their miraculous release (Acts 5:19). The word captures the physical reality of confinement, emphasizing the restriction of liberty under authority.

Beyond its literal sense of a jail, phulakē also denotes the act or state of keeping watch. It can refer to the guards themselves, as seen when Peter is escorted past them in chains (Acts 12:10), or to specific periods of the night during which these watches were kept. The Gospels record Jesus speaking about the fourth watch (Matthew 14:25) and calling his followers to be ready at any hour (Matthew 24:43), reflecting the Roman division of the night into four segments that had become standard in the first century.

Its root verb, phulassō, means to keep or protect. The lexica note that the Septuagint often uses this family of words for Hebrew terms related to keeping watch or guarding a place. This background adds depth to its New Testament usage, where imprisonment is not just a legal penalty but also a state of being kept in custody. Translators typically render it as "prison" when referring to the location and "watch" when indicating time or personnel, ensuring the context clarifies whether the focus is on confinement or vigilance.